Solar power generation system

ABSTRACT

A solar power generation system includes a string, an inverter, a first shutoff device, and a second shutoff device. The string includes a plurality of solar cell modules connected in series. The first shutoff device turns OFF, in response to a first control signal from the inverter, a first switching unit and a second switching unit. The first switching unit is connected to an anode side terminal of the string and an anode side terminal of the inverter. The second switching unit is connected to a cathode side terminal of the string and a cathode side terminal of the inverter. The second shutoff device is configured to output a second state signal to the first shutoff device and cut off a solar cell module group and either another solar cell module or the inverter, in response to a second control signal from the first shutoff device.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No.2022-026171, filed Feb. 22, 2022. The contents of that application areincorporated by reference herein in their entirety.

FIELD

The present invention relates to a solar power generation system.

BACKGROUND

Some solar power generation systems are equipped with a function that isconfigured to immediately stop the power generation in an emergency, forthe purpose of protecting firefighters from electric shock in anemergency such as a fire (for example, see Published JapaneseTranslation No. 2012-511299 of the PCT International Publication). Thefunction is called rapid shutdown function, which is executed by ashutoff device configured to cut off the electric path of the solarpower generation system in response to a control signal generated in anemergency.

SUMMARY

In a solar power generation system, a shutoff device is connected to anelectric path for an anode side terminal of a group including one or aplurality of series-connected solar cell modules and an electric pathfor a cathode side terminal of the group. However, the conventionalshutoff device is configured to cut off one of the two electric paths.Such configuration leaves an issue related to safety in an emergency.

An object of the present invention is to improve the safety of a solarpower generation system.

A solar power generation system according to one aspect of the presentinvention includes a string, an inverter, a first shutoff device, and asecond shutoff device. The string includes a plurality of solar cellmodules connected in series. The inverter is connected to the string andconfigured to convert DC power output from the string to AC power. Thefirst shutoff device includes a first switching unit connected to ananode side terminal of the string and an anode side terminal of theinverter, and a second switching unit connected to a cathode sideterminal of the string and a cathode side terminal of the inverter. Thefirst shutoff device is configured to turn OFF the first switching unitand the second switching unit in response to a first control signal fromthe inverter. The second shutoff device is connected to an electric pathconnecting a solar cell module group and either another solar cellmodule or the inverter. The solar cell module group includes one or aplurality of solar cell modules connected in series in the string. Thesecond shutoff device is configured to cut off the solar cell modulegroup and either the another solar cell module or the inverter inresponse to a second control signal from the first shutoff device andoutput a second state signal to the inverter or the first shutoff devicein response to a second control signal from the first shutoff device.

In the solar power generation system, the first shutoff device includesa first switching unit connected to an anode side terminal of the stringand an anode side terminal of the inverter, and a second switching unitconnected to a cathode side terminal of the string and a cathode sideterminal of the inverter, and turns OFF the first switching unit and thesecond switching unit in response to a first control signal from theinverter. That is, the first shutoff device is configured to cut off, inresponse to a first control signal from the inverter, both the electricpath connecting the anode side terminal of the string and the anode sideterminal of the inverter and the electric path connecting the cathodeside terminal of the string and the cathode side terminal of theinverter. The configuration enables the cutoff of both of the twoelectric paths connecting the string and the inverter, assuring reliableelectrical cutoff of the string and the inverter. As a result, it ispossible to improve the safety of the solar power generation system inan emergency. Further, the first shutoff device or the inverter canmonitor whether the second shutoff device is operating normally.

When the inverter or the first shutoff device determines that the secondshutoff device is abnormal depending on the second state signal outputfrom the second shutoff device, the inverter or the first shutoff devicemay output an abnormal signal. In this case, the inverter or the firstshutoff device can notify the user or the like of an abnormality in thesecond shutoff device.

The second shutoff device may output the second state signal to theinverter or the first shutoff device by power line communication.

The second shutoff device may output the second state signal to theinverter or the first shutoff device by wireless communication.

The second shutoff device may include an open-close unit configured toopen and close a connection between the solar cell module group and theanother solar cell module. The second state signal output from thesecond shutoff device may include information about an opened or closedstate of the open-close unit. In this case, for example, the inverter orthe first shutoff device can monitor whether the open-close unit isoperating normally.

The inverter may be configured to monitor the first shutoff device basedon a first state signal output from the first shutoff device. In thiscase, the inverter can monitor whether the first shutoff device isoperating normally.

When the inverter determines that the first shutoff device is abnormaldepending on the first state signal, the inverter may output an abnormalsignal. In this case, the inverter can notify the user or the like of anabnormality in the first shutoff device.

The second shutoff device may include a third switching unit connectedto an electric path connecting an anode side terminal of the solar cellmodule group and either the another solar cell module or the inverterand a fourth switching unit connected to an electric path connecting acathode side terminal of the solar cell module group and either theanother solar cell module or the inverter. In this case, the secondshutoff device is able to cut off both of an electric path connecting ananode side terminal of the solar cell module group and either theanother solar cell module or the inverter (hereinafter referred to as“the other device”) and the electric path connecting a cathode sideterminal of the solar cell module group and the other device. As aresult, it is possible to improve the safety of the solar powergeneration system in an emergency.

The second shutoff device may include a bypass device connected inparallel with the solar cell module group and configured to form anelectric path bypassing the solar cell module group. In this case, whenan abnormality occurs in the solar cell module group, it is possible forthe power generated by the another solar cell module to bypass thebypass device to be supplied to the inverter.

The bypass device may be a diode having an anode connected to thecathode side terminal of a solar cell module group and a cathodeconnected to the anode side terminal of the solar cell module group. Inthis case, when an abnormality occurs in the solar cell module group, anelectric path bypassing said solar cell module group can be immediatelyformed without any instruction by an external signal.

The first shutoff device may be driven by power supplied from acommercial power supply. In this case, the first shutoff device is ableto operate whether or not power is supplied thereto from the string. Asa result, the string and the inverter can be reliably cut off in anemergency, and thereby the safety of the solar power generation systemin an emergency can be improved.

The second shutoff device may be driven by power generated by at leastone of the plurality of solar cell modules. In this case, the powergenerated by the solar cell modules can be used effectively to drive thesecond shutoff device.

The inverter may output the first control signal to the first shutoffdevice by power line communication. In this case, no separate wiring forcommunication between the inverter and the first shutoff device isnecessary.

The inverter may output the first control signal to the first shutoffdevice by wireless communication. In this case, no wiring forcommunication between the inverter and the first shutoff device isnecessary.

The first shutoff device may output the second control signal to thesecond shutoff device by power line communication, upon receipt of thefirst control signal from the inverter. In this case, no separate wiringfor communication between the first shutoff device and the secondshutoff device is necessary.

The first shutoff device may output the second control signal to thesecond shutoff device by wireless communication, upon receipt of thefirst control signal from the inverter. In this case, no wiring forcommunication between the first shutoff device and the second shutoffdevice is necessary.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a configuration of a solar power generationsystem.

FIG. 2 is a diagram showing a configuration of a first shutoff device.

FIG. 3 is a diagram showing a configuration of a second shutoff device.

FIG. 4 is a diagram showing another example of connection of a bypassdevice in a second shutoff device.

FIG. 5 is a diagram showing a state of a first shutoff device in eachoperation mode.

FIG. 6 is a diagram showing a state of a second shutoff device in eachoperation mode.

FIG. 7 is a diagram showing another configuration of solar cell modulegroups in a string.

FIG. 8 is a diagram showing another configuration of solar cell modulegroups in a string.

DETAILED DESCRIPTION

A solar power generation system 1 is described with reference to FIG. 1. FIG. 1 is a diagram showing a configuration of the solar powergeneration system 1. The solar power generation system 1 includes astring 2, an inverter 3, a first shutoff device 4, and second shutoffdevices 5A to 5D.

The string 2 includes a plurality of solar cell modules 6 connected inseries. The string 2 of the present embodiment includes 16 solar cellmodules 6. It should be noted that the solar power generation system 1may include a solar cell array in which a plurality of strings 2 areconnected in parallel.

The string 2 includes a plurality of solar cell module groups. Each ofthe plurality of solar cell module groups includes one or a plurality ofa plurality of series-connected solar cell modules 6. The solar cellmodule group each have an anode side terminal and a cathode sideterminal. In a group consisted of one solar cell module 6, the anode ofthe solar cell module 6 provides the anode side terminal of said group,and the cathode of the solar cell module 6 provides the cathode sideterminal of said group.

In a group including a plurality of solar cell modules 6, among theplurality of series-connected solar cell modules 6, the anode sideterminal of said group is configured by the anode of the solar cellmodule 6 closest to the anode of the inverter 3, and the cathode sideterminal of said group is configured by the cathode of the solar cellmodule 6 closest to the cathode of the inverter 3. In FIG. 1 , the anodeside terminal of each solar cell module group is indicated by “+”, andthe cathode side terminal is indicated by “−”.

The string 2 includes eight solar cell module groups in total: a firstsolar cell module group 6A to an eighth solar cell module group 6H. Thefirst group 6A, the third group 6C, the fifth group 6E, and the seventhgroup 6G each include one solar cell module 6. The second group 6B, thefourth group 6D, the sixth group 6F, and the eighth group 6H eachinclude three solar cell modules 6.

The first group 6A to the eighth group 6H are connected in series in thestring 2. Specifically, the cathode side terminal of the first group 6Ais connected to the anode side terminal of the second group 6B. Thecathode side terminal of the second group 6B is connected to the anodeside terminal of the third group 6C. The cathode side terminal of thethird group 6C is connected to the anode side terminal of the fourthgroup 6D. The cathode side terminal of the fourth group 6D is connectedto the anode side terminal of the fifth group 6E. The cathode sideterminal of the fifth group 6E is connected to the anode side terminalof the sixth group 6F. The cathode side terminal of the sixth group 6Fis connected to the anode side terminal of the seventh group 6G. Thecathode side terminal of the seventh group 6G is connected to the anodeside terminal of the eighth group 6H. It should be noted that the anodeside terminal of the first group 6A is connected to the anode sideterminal of the inverter 3. The cathode side terminal of the eighthgroup 6H is connected to the cathode side terminal of the inverter 3.

The solar cell modules 6 receive sunlight and generate power. The solarcell modules 6 have an open circuit voltage of 50 V, for example. Theinverter 3 is connected to the string 2 via a power line. The inverter 3converts DC power output from the string 2 in which the plurality ofsolar cell modules 6 are connected in series into AC power. The inverter3 is connected to a power system 7 and supplies the AC power tocommercial power systems and load devices.

Specifically, the inverter 3 includes a DC/DC converter 3 a, a DC/ACinverter 3 b, a control unit 3 c, and a first control signal generatingunit 3 d. The DC/DC converter 3 a converts the voltage of the poweroutput from the string 2 into a predetermined voltage and inputs it tothe DC/AC inverter 3 b. The DC/AC inverter 3 b converts the DC poweroutput from the DC/DC converter 3 a into AC power.

The control unit 3 c is a computer system including a CPU, memory, andvarious interface. The control unit 3 c controls the DC/DC converter 3 aand the DC/AC inverter 3 b. The control unit 3 c may control the DC/DCconverter 3 a and the DC/AC inverter 3 b by executing a program storedin a storage device. The first control signal generating unit 3 doutputs a first control signal S1 to the first shutoff device 4 by powerline communication when an operation switch 8 is pressed.

The first shutoff device 4 is connected to a power line connectingbetween the string 2 and the inverter 3. The first shutoff device 4 cutsoff the string 2 and the inverter 3 in response to the first controlsignal S1 from the inverter 3.

The second shutoff devices 5A to 5D are each connected to an electricpath connecting one solar cell module group and another solar cellmodule, or an electric path connecting one solar cell module group andthe inverter 3.

Specifically, the second shutoff device 5A is connected to an electricpath connecting the anode side terminal of the first group 6A and thefirst shutoff device 4, and also to an electric path connecting thecathode side terminal of the first group 6A and the anode side terminalof the second group 6B. The second shutoff device 5B is connected to anelectric path connecting the anode side terminals of the third group 6Cand the cathode side terminals of the second group 6B, and also to anelectric path connecting the cathode side terminals of the third group6C and the anode side terminal of the fourth group 6D. The secondshutoff device 5C is connected to an electric path connecting the anodeside terminals of the fifth group 6E and the cathode side terminals ofthe fourth group 6D, and also to an electric path connecting the cathodeside terminals of the fifth group 6E and the anode side terminal of thesixth group 6F. The second shutoff device 5D is connected to an electricpath connecting the anode side terminals of the seventh group 6G and thecathode side terminals of the sixth group 6F, and also to an electricpath connecting the cathode side terminals of the seventh group 6G andthe anode side terminal of the eighth group 6H.

In response to the second control signal S2 from the first shutoffdevice 4, each of the second shutoff devices 5A to 5D cuts off the solarcell module group to which the device itself is connected and the othersolar cell modules, or cuts off the solar cell module group to which thedevice itself is connected and the inverter 3. In response to the secondcontrol signal S2 from the first shutoff device 4, each of the secondshutoff devices 5A to 5D outputs a second state signal to the firstshutoff device.

A specific configuration of the first shutoff device 4 will be describedbelow with reference to FIG. 2 . FIG. 2 is a diagram showing aconfiguration of the first shutoff device 4. The first shutoff device 4includes a first switching unit 4 a, a second switching unit 4 b, afirst signal receiving unit 4 c, a first driving unit 4 d, and a firstsignal sending unit 4 e.

The first switching unit 4 a has one end connected to the anode sideterminal of the string 2 and the other end connected to the anode sideterminal of the inverter. The anode side terminal of the string 2corresponds to the anode of the solar cell module 6 in the first group6A. The second switching unit 4 b has one end connected to the cathodeside terminal of the string 2 and the other end connected to the cathodeside terminal of the inverter. The cathode side terminal of the string 2corresponds to the cathode of the solar cell module 6, among the solarcell modules 6 in the eighth group 6H, closest to the cathode sideterminal of the inverter 3. The first switching unit 4 a and the secondswitching unit 4 b are switching devices, for example, relays orsemiconductor switches such as MOSFETs.

In the present embodiment, the first switching unit 4 a and the secondswitching unit 4 b are simultaneously switched between the ON state andthe OFF state under the control of the first driving unit 4 d. As aresult, it is possible to simultaneously cut off the power lineconnecting the anode side terminal of the string 2 and the anode sideterminal of the inverter 3 and the power line connecting the cathodeside terminal of the string 2 and the cathode side terminal of theinverter 3.

It should be noted that “turn the switching unit ON” means that theswitching unit is made conductive to make the power line or the electricpath, to which the switching unit is connected, electrically conductive.In contrast, “turn the switching unit OFF” means that the switching unitis made insulated to make the power line or electric path, to which theswitching unit is connected, electrically cut off.

In addition, the first switching unit 4 a and the second switching unit4 b may be independently supplied with a drive signal from the firstdriving unit 4 d to be switched between the ON state and the OFF stateindependently of each other. Accordingly, the types of cutoffcombinations can be increased using the power line connecting the anodeside terminal of the string 2 and the anode side terminal of theinverter 3 and the power line connecting the cathode side terminal ofthe string 2 and the cathode side terminal of the inverter 3. Forexample, both of the above two power lines can be cut off, and one ofthe two power lines can be cut off as well. As a result, even if one ofthe switching units does not operate properly, the string 2 and theinverter 3 can be reliably cut off by cutting off one power line byanother switching unit.

The first signal receiving unit 4 c receives a first control signal S1output from the inverter 3. Upon receiving the first control signal S1,the first signal receiving unit 4 c outputs, to the first driving unit 4d, a signal indicating that the first control signal S1 has beenreceived. In the present embodiment, the first control signal S1 isoutput by power line communication to the power line connecting theinverter 3 and the first shutoff device 4. Thus, the first signalreceiving unit 4 c is, for example, a signal receiving circuitconfigured to extract a signal sent by power line communication from thepower line.

The first driving unit 4 d outputs a drive signal for driving the firstswitching unit 4 a and the second switching unit 4 b, to the firstswitching unit 4 a and the second switching unit 4 b. When the string 2is connected to the inverter 3, the first driving unit 4 d outputs adrive signal for closing and turning ON the first switching unit 4 a andthe second switching unit 4 b, to the first switching unit 4 a and thesecond switching unit 4 b. In contrast, upon receiving a signalindicating that the first control signal S1 has been received from thefirst signal receiving unit 4 c, the first driving unit 4 d stopsoutputting the drive signal, and opens and turns OFF the first switchingunit 4 a and the second switching unit 4 b. With the configuration, thefirst switching unit 4 a and the second switching unit 4 b are able tocut off the string 2 and the inverter 3 in response to the first controlsignal S1.

On the contrary to the above configuration, the first switching unit 4 aand the second switching unit 4 b may be turned OFF upon receipt of adrive signal from the first driving unit 4 d. In this case, the firstdriving unit 4 d outputs a drive signal when receiving from the firstsignal receiving unit 4 c a signal indicating that the first controlsignal S1 has been received, and turns OFF the first switching unit 4 aand the second switching unit 4 b. When not receiving the signalindicating that the first control signal S1 has been received, the firstdriving unit 4 d stops outputting the drive signal, and turns ON thefirst switching unit 4 a and the second switching unit 4 b.

The first driving unit 4 d is, for example, a signal generating circuitconfigured to generate a signal for driving the first switching unit 4 aand the second switching unit 4 b upon receipt of a signal from thefirst signal receiving unit 4 c.

When cutting off the string 2 and the inverter 3 in response to thefirst control signal S1, the first driving unit 4 d outputs, to thefirst signal sending unit 4 e, a signal indicating that the string 2 andthe inverter 3 have been cut off. The first signal sending unit 4 e,when receiving the signal indicating that the string 2 and the inverter3 have been cut off, outputs a second control signal S2 to the powerline connecting the first shutoff device 4 and the string 2. In thepresent embodiment, the first signal sending unit 4 e outputs the secondcontrol signal S2 to the power line connecting the first shutoff device4 and the string 2 by power line communication. Thus, the first signalsending unit 4 e is, for example, a signal generating circuit configuredto generate and output a signal to be sent by power line communication.

The first shutoff device 4 is driven by an external commercial powersupply 9. Specifically, the first driving unit 4 d uses AC powersupplied from the commercial power supply 9 to generate a signal fordriving the first switching unit 4 a and the second switching unit 4 b.For example, the first driving unit 4 d converts the AC power from thecommercial power supply 9 into DC power to generate drive power. Thefirst signal receiving unit 4 c and the first signal sending unit 4 eare also driven by the AC power supplied from the commercial powersupply 9. These configurations allow the first shutoff device 4 tooperate regardless of whether power is supplied from the string 2 ornot.

A specific configuration of the second shutoff devices 5A to 5D will bedescribed below with reference to FIG. 3 . FIG. 3 is a diagram showing aconfiguration of the second shutoff devices 5A to 5D. The second shutoffdevices 5A to 5D have an identical configuration. Thus, theconfiguration of the second shutoff device 5A will be described in thefollowing as an example. The second shutoff device 5A includes a thirdswitching unit 5 a, a fourth switching unit 5 b, a second signalreceiving unit 5 c, a bypass circuit 5 d, a power supply unit 5 e, asecond driving unit 5 f, and a bypass device 5 g.

The third switching unit 5 a has one end connected to the anode sideterminal of the first group 6A and the other end connected to the firstshutoff device 4. The fourth switching unit 5 b has one end connected tothe cathode side terminal of the first group 6A and the other endconnected to the anode side terminal of the second group 6B. The thirdswitching unit 5 a and the fourth switching unit 5 b are switchingdevices, such as relays or semiconductor switches such as MOSFETs. Thefourth switching unit 5 b in the present embodiment is an example of anopen-close unit.

In the present embodiment, the third switching unit 5 a and the fourthswitching unit 5 b are simultaneously switched between the ON state andthe OFF state under the control of the second driving unit 5 f. With theconfiguration, the second shutoff device 5A is able to simultaneouslycut off the electric path connecting the anode side terminal of thefirst group 6A and the first shutoff device 4 and the electric pathconnecting the cathode side terminal of the first group 6A and the anodeside terminal of the second group 6B.

In addition, the third switching unit 5 a and the fourth switching unit5 b may be independently supplied with the drive signal from the seconddriving unit 5 f to be switched between the ON state and the OFF stateindependently of each other. With the configuration, the second shutoffdevice 5A is able to increase the types of cutoff combinations using theelectric path connecting the anode side terminal of the first group 6Aand the first shutoff device 4 and the electric path connecting thecathode side terminal of the first group 6A and the anode side terminalof the second group 6B. For example, both of the above two electricpaths can be cut off, and only one of the two electric paths can be cutoff as well. As a result, even if one of the switching units does notoperate properly, the first group 6A and the other device can be cut offby cutting off one electric path by another switching unit.

The second signal receiving unit 5 c receives the second control signalS2 output from the first shutoff device 4. The second signal receivingunit 5 c, when receiving the second control signal S2, outputs to thesecond driving unit 5 f a signal indicating that the second controlsignal S2 has been received. In the present embodiment, the secondcontrol signal S2 is output, by power line communication, to theelectric path connecting the first shutoff device 4 and the secondshutoff device 5A. Thus, the second signal receiving unit 5 c is, forexample, a signal receiving circuit configured to extract a signal sentby power line communication from an electric path.

The bypass circuit 5 d is a circuit that is configured to transmit thesecond control signal S2 sent via one electric path to the otherelectric path in the second shutoff device 5A. Specifically, the bypasscircuit 5 d transmits the second control signal S2 sent via the electricpath, to which the first shutoff device 4 is connected, to the electricpath connecting the cathode side terminal of the first group 6A and theanode side terminal of the second group 6B.

In the present embodiment, the second control signal S2 is transmittedthrough the electric paths by power line communication. That is, thesecond control signal S2 is a signal of a predetermined frequency.Accordingly, the bypass circuit 5 d is a circuit configured to passsignals of a predetermined frequency. Specifically, the bypass circuit 5d is, for example, a high-pass filter circuit configured to pass signalsof frequencies equal to or higher than the predetermined frequency, or aband-pass filter circuit configured to pass only signals of thepredetermined frequency. The bypass circuit 5 d, which is a high-passfilter, can be implemented by a capacitor element, for example.

The power supply unit 5 e uses the power generated by the solar cellmodule included in the first group 6A to generate power to drive thesecond shutoff device 5A. When DC power is used as power for driving thesecond shutoff device 5A, the power supply unit 5 e is, for example, aregulator circuit.

The second driving unit 5 f outputs a drive signal, to the thirdswitching unit 5 a and the fourth switching unit 5 b, for driving thethird switching unit 5 a and the fourth switching unit 5 b. The seconddriving unit 5 f uses the power supplied from the power supply unit 5 eto generate the drive signal and outputs it to the third switching unit5 a and the fourth switching unit 5 b.

When it is desired to connect the solar cell module groups to which thesecond shutoff device 5A is connected to the other device, the seconddriving unit 5 f outputs a drive signal to the third switching unit 5 aand the fourth switching unit 5 b to close and turn ON the thirdswitching unit 5 a and the fourth switching unit 5 b.

In contrast, upon receipt of a signal indicating that the second controlsignal S2 has been received from the second signal receiving unit 5 c,the second driving unit 5 f stops outputting the drive signal and opensand turns OFF the third switching unit 5 a and the fourth switching unit5 b. With the configuration, the third switching unit 5 a and the fourthswitching unit 5 b are able to cut off the solar cell module groups andthe other device in response to the second control signal S2. The seconddriving unit 5 f outputs the second state signal including informationthat the output of the drive signal has been stopped in response to thesecond control signal S2 to the first shutoff device 4 by power linecommunication.

On the contrary to the above configuration, the third switching unit 5 aand the fourth switching unit 5 b may be turned OFF upon receipt of adrive signal from the second driving unit 5 f. In this case, the seconddriving unit 5 f outputs a drive signal when receiving a signalindicating that the second control signal S2 has been received from thesecond signal receiving unit 5 c, and turns OFF the third switching unit5 a and the fourth switching unit 5 b. When not receiving the signalindicating that the second control signal S2 has been received, thesecond driving unit 5 f stops outputting the drive signal to turn ON thethird switching unit 5 a and the fourth switching unit 5 b.

The second driving unit 5 f is, for example, a signal generating circuitconfigured to, when receiving a signal from the second signal receivingunit 5 c, generate a signal for driving the third switching unit 5 a andthe fourth switching unit 5 b, using the power supplied from the powersupply unit 5 e.

The second control signal S2 is output, after the first shutoff device 4receives the first control signal S1 and cuts off the string 2 and theinverter 3. Accordingly, the shutoff of the electric paths by the secondshutoff device 5A are performed after the string 2 and the inverter 3are cut off.

The bypass device 5 g is connected in parallel with the first group 6Ato which the second shutoff device 5A is connected. The bypass device 5g forms an electric path bypassing the solar cell module groups to whichthe second shutoff device 5A is connected. As shown in FIG. 3 , thebypass device 5 g is a diode having an anode connected to the cathodeside terminal of the first group 6A and a cathode connected to the anodeside terminal of the first group 6A.

When an abnormality such as a sudden power drop or unusual heatgeneration occurs at the first group 6A to which the second shutoffdevice 5A is connected and the first group 6A cannot output sufficientpower, the bypass device 5 g forms an electric path that “bypasses” thedefective first group 6A so as to transfer the power generated byanother solar cell module group. Specifically, when an abnormalityoccurs in the first group 6A, the bypass device 5 g of the secondshutoff device 5A forms a path to transfer the power, which is generatedby the second group 6B to the eighth group 6H, from the second group 6Bto the inverter 3 (the first shutoff device 4).

When the first group 6A becomes unable to output sufficient power, thebypass device 5 g, which is a diode, is able to instantly form anelectric path that bypasses the defective first group 6A based on itselectrical characteristics without an external signal command.

It should be noted that the two terminals of the bypass device 5 g canbe connected to any point as desired as long as the first group 6A towhich the second shutoff device 5A is connected is bypassed and also atleast one of the terminals of the bypass device 5 g is connected to thefirst group 6A without connection to the third switching unit 5 a or thefourth switching unit 5 b. For example, as shown in FIG. 4 , aconfiguration is possible in which the anode of the bypass device 5 g isconnected to the electric path connecting the anode side terminal of thesecond group 6B and the fourth switching unit 5 b and the cathode of thebypass device 5 g is connected to the electric path connecting the anodeside of the first group and the third switching unit 5 a. FIG. 4 is adiagram showing another example of connection of the bypass device 5 gin the second shutoff device 5A.

The first shutoff device 4 monitors the second shutoff devices 5A to 5Dbased on the second state signals output from the second shutoff devices5A to 5D. The first shutoff device 4 outputs an abnormal signal to theinverter 3 when determining that the second shutoff devices 5A to 5D areabnormal depending on the second state signals output from the secondshutoff devices 5A to 5D. The first shutoff device 4 determines that thesecond shutoff devices 5A to 5D are abnormal when, for example, thesecond state signals from the second shutoff devices 5A to 5D inresponse to the second control signal S2 cannot be received. When theinverter 3 receives the abnormal signal from the first shutoff device 4,the inverter 3 notifies that the second shutoff devices 5A to 5D areabnormal via a display unit 10 connected to the inverter 3.

Next, an example of the operations of the first shutoff device 4 and thesecond shutoff devices 5A to 5D will be described with reference toFIGS. 5 and 6 . FIG. 5 is a diagram showing the state of the firstshutoff device 4 in each operation mode. FIG. 6 shows the state of thesecond shutoff devices 5A to 5D in each operation mode. The solar powergeneration system 1 has three operation modes: a start mode, an activemode, and a safety mode. The safety mode includes a normal shutoff modeand an emergency safety shutoff mode.

The start mode is a mode that turns effective when sunlight starts tohit the solar cell modules 6. At this time, the solar cell modules 6receive sunlight to generate power. In the start mode, the inverter 3outputs no first control signal S1 (the first control signal “NONE”),and thereby the first driving unit 4 d outputs a drive signal to thefirst switching unit 4 a and the second switching unit 4 b in the firstshutoff device 4. As a result, the first switching unit 4 a and thesecond switching unit 4 b are turned ON (the relay operation mode “ON”),and the string 2 and the inverter 3 are connected. Since no firstcontrol signal S1 is output, the first signal sending unit 4 e outputsno second control signal S2.

In the second shutoff devices 5A to 5D, the power supply unit 5 e usesthe power generated in the solar cell module groups to generate power todrive the second shutoff devices 5A to 5D. Also, since the first shutoffdevice 4 outputs no second control signal S2 (the second control signal“NONE”), the second driving unit 5 f uses the power generated by thepower supply unit 5 e to generate a drive signal and outputs it to thethird switching unit 5 a and the fourth switching unit 5 b. As a result,the third switching unit 5 a and the fourth switching unit 5 b areturned ON (the relay operation mode “ON”), and the solar cell modulegroups connected to the second shutoff devices 5A to 5D are connected tothe other device.

As described above, the power generated in the string 2 is supplied tothe inverter 3 via the first shutoff device 4 in the start mode. The DCpower supplied from the string 2 is converted into AC power by theinverter 3 and supplied to the power system 7.

The active mode is a state in which the solar cell modules 6 receivesunlight during the day to generate power, and is substantially the sameas the start mode. Specifically, in the active mode, no first controlsignal S1 is output (the first control signal “NONE”), and the firstswitching unit 4 a and the second switching unit 4 b of the firstshutoff device 4 are in the ON state (the relay operation mode “ON”). Inaddition, no second control signal S2 is output (the second controlsignal “NONE”), and the third switching unit 5 a and the fourthswitching unit 5 b of the second shutoff devices 5A to 5D are in the ONstate. As a result, the power generated in the string 2 is supplied tothe inverter 3 via the first shutoff device 4. The DC power suppliedfrom the string 2 is converted into AC power by the inverter 3 andsupplied to the power system 7.

The normal shutoff mode is a mode when the solar cell modules 6 are notexposed to sunlight at night or due to the influence of bad weather suchas rain. Accordingly, in the normal shutoff mode, the solar cell modules6 do not generate power. In the normal shutoff mode, the inverter 3outputs the first control signal S1 (the first control signal“PRESENT”). Thus, the first switching unit 4 a and the second switchingunit 4 b of the first shutoff device 4 are in the OFF state (the relayoperation mode “OFF”).

In the second shutoff devices 5A to 5D, the second control signal S2 isoutput (the second control signal “PRESENT”), and the third switchingunit 5 a and the fourth switching unit 5 b are in the OFF state (therelay operation mode “OFF”). It should be noted that, in the normalshutoff mode, the second shutoff devices 5A to 5D are not supplied withthe power from the solar cell module groups, and thereby no drivingsignal cannot be generated to be output from the second driving unit 5 fto the third switching unit 5 a and the fourth switching unit 5 b.

In the normal shutoff mode, when the power generation by the solar cellmodules 6 is unstable due to unstable weather or the like, no firstcontrol signal S1 is output (the first control signal “NONE”), and thefirst switching unit 4 a and the second switching unit 4 b of the firstshutoff device 4 are in the ON state (the relay operation mode “ON”). Incontrast, in the second shutoff devices 5A to 5D, no second controlsignal S2 is output (the second control signal “NONE”), and the thirdswitching unit 5 a and the fourth switching unit 5 b are in the ON/OFFstate (the relay operation mode “ON/OFF”) according to the powersupplied from the solar cell module groups connected to the secondshutoff devices 5A to 5D.

With the configuration described above, in the normal shutoff mode,either the string 2 cannot supply power to the inverter 3 or the powersupply to the inverter 3 is cut off frequently.

The emergency safety shutoff mode is a mode in which the power supplyfrom the string 2 to the inverter 3 is cut off during the start mode orthe active mode. The emergency safety shutoff mode starts when theoperation switch 8 is operated in the start mode or the active mode.

Specifically, with an operation of the operation switch 8, the firstcontrol signal generating unit 3 d of the inverter 3 sends the firstcontrol signal S1 to the first shutoff device 4 by power linecommunication (the first control signal “PRESENT”). Thus, in the presentembodiment, the first control signal S1 is output only at the start ofthe emergency safety shutdown mode.

When the first signal receiving unit 4 c receives the first controlsignal S1, the first driving unit 4 d stops outputting drive power tothe first switching unit 4 a and the second switching unit 4 b. As aresult, the first switching unit 4 a and the second switching unit 4 bare turned OFF, and the string 2 and the inverter 3 are cut off (therelay operation mode “OFF”). At the timing when the first switching unit4 a and the second switching unit 4 b are turned OFF, the first signalsending unit 4 e outputs the second control signal S2 to the string 2 bypower line communication (the second control signal is “PRESENT”).

When the second signal receiving unit 5 c of the second shutoff devices5A to 5D receives the second control signal S2, the second driving unit5 f stops outputting driving power to the third switching unit 5 a andthe fourth switching unit 5 b. As a result, the third switching unit 5 aand the fourth switching unit 5 b are turned OFF, and the solar cellmodule groups and the other device connected to the second shutoffdevices 5A-5B are cut off (the relay operation mode “OFF”). That is, thevoltages output from all the solar cell modules 6 included in the string2 are cut off. When the second driving unit 5 f receives the secondcontrol signal S2 and stops outputting the driving signals to drive thethird switching unit 5 a and the fourth switching unit 5 b, the seconddriving unit 5 f outputs the second state signal including informationthat the output of the drive signal to the third switching unit 5 a andthe fourth switching unit 5 b has been stopped to the first shutoffdevice 4. The first shutoff device 4 determines that the second shutoffdevices 5A to 5D are abnormal when the second state signals from thesecond shutoff devices 5A to 5D in response to the second control signalS2 cannot be received.

As described above, in the emergency safety shutoff mode, the firstshutoff device 4 is able to shutoff the string 2 and the inverter 3, andthe second shutoff devices 5A to 5D are able to cut off the solar cellmodule groups in the string 2 by group. Specifically, the second shutoffdevice 5A cuts off the connection between the first group 6A and thesecond group 6B. The second shutoff device 5B cuts off the connectionbetween the second group 6B and the third group 6C and the connectionbetween the third group 6C and the fourth group 6D. The second shutoffdevice 5C cuts off the connection between the fourth group 6D and thefifth group 6E and the connection between the fifth group 6E and thesixth group 6F. The second shutoff device 5D cuts off the connectionbetween the sixth group 6F and the seventh group 6G and the connectionbetween the seventh group 6G and the eighth group 6H.

With the configuration, in the solar power generation system 1, theinstallation cost of the shutoff devices can be reduced compared withthe case where a shutoff device is installed for each solar cell module6. In addition, in the emergency safety shutoff mode, not only thestring 2 is cut off for each solar cell module group, but also theconnection between the string 2 and the inverter 3 is cut off, andthereby a solar power generation system with higher safety can beprovided.

In the solar power generation system1, the first shutoff device 4includes the first switching unit 4 a connected to the anode sideterminal of the string 2 and the anode side terminal of the inverter 3,and the second switching unit 4 b connected to the cathode side terminalof the string 2 and the cathode side terminal of the inverter 3, so thatthe first switching unit 4 a and the second switching unit 4 b areturned OFF in response to a first control signal S1 from the inverter 3.That is, the first shutoff device 4 is able to cut off both of the powerline connecting the anode side terminal of the string 2 and the anodeside terminal of the inverter 3 and the power line connecting thecathode side terminal of the string 2 and the cathode side terminal ofthe inverter 3, in response to the first control signal S1. In this way,the first shutoff device 4 is configured to cut off both of the twopower lines connecting the string 2 and the inverter 3, leading toreliable electrical cutoff of the string 2 and the inverter 3. As aresult, it is possible to improve the safety of the solar powergeneration system 1 in an emergency.

The second shutoff devices 5A to 5D include the third switching unit 5 aconnected to an electric path connecting the anode side terminal of asolar cell module group and either another solar cell module group 6 orthe inverter 3, and the fourth switching unit 5 b connected to anelectric path connecting the cathode side terminal of the solar cellmodule group and either another solar cell module group 6 or theinverter 3. With the configuration, in the second shutoff devices 5A to5D, both of the electric path connecting the anode side terminal of asolar cell module group and another solar cell module group or inverter3 and the electric path connecting the cathode side terminal of thesolar cell module group and either another solar cell module group 6 orthe inverter 3 are cut off. As a result, it is possible to improve thesafety of the solar power generation system 1 in an emergency.

Since each of the second shutoff devices 5A to 5D outputs the secondstate signal to the first shutoff device in response to the secondcontrol signal S2 from the first shutoff device 4, the first shutoffdevice 4 can detect that the second shutoff devices 5A to 5D areoperating normally when the operation switch 8 is operated. As a result,a further highly safe solar power generation system 1 can be provided.

The second shutoff devices 5A to 5D include the bypass device 5 g thatis connected in parallel with a solar cell module group to form anelectric path bypassing the solar cell module. With the configuration,when an abnormality occurs in the solar cell module group, powergenerated by the other solar cell modules bypasses the bypass device tobe supplied to the inverter 3.

The first shutoff device 4 is driven by the power supplied from acommercial power supply 9. Thus, the first shutoff device 4 is able tooperate regardless of whether power is supplied from the string 2 ornot. As a result, the string 2 and the inverter 3 can be reliably cutoff in an emergency, and thereby it is possible to improve the safety ofthe solar power generation system 1 in an emergency.

The second shutoff devices 5A to 5D are driven by the power generated bythe solar cell modules 6. As such, the power generated by the solar cellmodules 6 is used effectively to drive the second shutoff devices 5A to5D.

The inverter 3 outputs the first control signal S1 to the first shutoffdevice 4 by power line communication. As such, no separate line isnecessary for the communication between the inverter 3 and the firstshutoff device 4.

Upon receipt of the first control signal S1 from the inverter 3, thefirst shutoff device 4 may output the second control signal S2 to thesecond shutoff devices 5A to 5D by power line communication. With theoperation, no separate line is necessary for the communication betweenthe first shutoff device 4 and the second shutoff devices 5A to 5D.

One embodiment of the present invention has been described above, butthe present invention is not limited to the above embodiment, andvarious modifications can be made without departing from the gist of theinvention.

The group division of solar cell module groups in string 2 and thenumber of solar cell modules 6 included in each group can be determinedas needed, for example, based on the open-circuit voltage to be used forcutting off the string 2 during the emergency safety shutoff mode. Forexample, in the emergency safety shutoff mode, the open circuit voltageof string 2 is preferably divided to 165 V or less. When one solar cellmodule 6 has an open-circuit voltage of 50 V, it is preferable to cutoff the strings 2 into groups each including three solar cell modules 6.

For example, in the solar power generation system 1′ shown in FIG. 7 ,the string 2′ includes 18 solar cell modules 6 connected in series, andincludes six solar cell module groups 6A′ to 6F′. Each of the solar cellmodule groups 6A′ to 6F′ includes three serial solar cell modules 6.Further, the solar cell module groups 6A′, 6C, 6E′ are connected tosecond shutoff devices 5A′, 5B′, 5C, respectively. FIG. 7 is a diagramshowing another configuration of solar cell module groups in a string.

In the solar power generation system 1″ shown in FIG. 8 , for example,the string 2″ includes 12 solar cell modules 6 connected in series, andincludes four solar cell module groups 6A″ to 6D″. Each of the solarcell module group 6A″ to 6D″ includes three serial solar cell modules 6.Furthermore, the solar cell module groups 6A″ to 6D″ are connected tosecond shutoff devices 5A″ to 5D″, respectively. FIG. 8 is a diagramshowing another configuration of solar cell module groups in a string.

It should be noted that the solar power generation systems 1′ and 1″differ from the above solar power generation system 1 only in theconfiguration of the solar cell module groups in the strings 2′ and 2″.Other configurations of the solar power generation systems 1′ and 1″ arethe same as those of the solar power generation system 1.

The start mode or the active mode may be switched to the emergencysafety shutoff mode when an abnormality is detected in the output fromthe solar cell modules 6 in the string 2. In this case, for example, thesolar power generation system 1 may include a sensor that is configuredto detect an output of the solar cell module 6, so that when anabnormality is detected from the output of the solar cell module 6 bythe sensor, the first control signal generating unit 3 d of the inverter3 outputs the first control signal S1 to perform the switching to theemergency safety shutoff mode. Alternatively, for example, the inverter3 may be connected to a fire sensor or a fire alarm, so that when theinverter 3 receives a signal from the fire sensor or the fire alarm, thefirst control signal generating unit 3 d outputs the first controlsignal S1 to perform the switching to the emergency safety shutoff mode.

The first control signal S1 and/or the second control signal S2 can besent and received by methods other than power line communication. Forexample, the first control signal S1 and/or the second control signal S2may be sent and received by wireless communication. Alternatively, thefirst control signal S1 may be sent and received by power linecommunication, while the second control signal S2 may be sent andreceived by wireless communication. For sending and receiving the secondcontrol signal S2 by wireless communication, no bypass circuit 5 d isnecessary in the second shutoff device. Each of the second shutoffdevices 5A to 5D may output the second state signal to the first shutoffdevice 4 by wireless communication. Each of the second shutoff devices5A to 5D may be connected to the first shutoff device 4 in a two-waycommunicable manner by wireless communication. The first shutoff device4 may output the abnormal signal to the inverter 3 by wirelesscommunication. The first shutoff device 4 may be configured to outputthe abnormal signal to a user's mobile terminal by wirelesscommunication.

The second state signals output from the second shutoff devices 5A to 5Dmay include at least one of information about the voltage of the secondshutoff devices 5A to 5D, current of the second shutoff devices 5A to5D, or an opened or closed state of each the fourth switching unit 5 b.The first shutoff device 4 may determine that the second shutoff devices5A to 5D are abnormal based on the information about the opened orclosed state of each the fourth switching unit 5 b. When each the fourthswitching unit 5 b is composed of a mechanical relay, the first shutoffdevice 4 may determine the second shutoff devices 5A to 5D are abnormalby monitoring the voltage between the contacts of each the fourthswitching unit 5 b based on the second state signals output from thesecond shutoff devices 5A to 5D to detect welding of each the fourthswitching unit 5 b. When the second state signals output from the secondshutoff devices 5A to 5D include the information about the opened orclosed state of each the fourth switching unit 5 b, the second statesignals output from the second shutoff devices 5A to 5D may furtherinclude information about the opened or closed state of each the thirdswitching unit 5 a. The second state signals output from the secondshutoff devices 5A to 5D may include information indicating that thesecond shutoff devices 5A to 5D are abnormal. That is, the secondshutoff devices 5A to 5D may be configured to monitor their own voltageand the like and detect abnormalities in the second shutoff devices 5Ato 5D themselves.

In the above embodiment, the second shutoff devices 5A to 5D areconfigured to output the second state signals to the first shutoffdevice 4 in response to the second control signal S2 from the firstshutoff device 4. However, the second shutoff devices 5A to 5D mayoutput the second state signals to the first shutoff device 4periodically or constantly in the active mode when the second statesignals output from the second shutoff devices 5A to 5D include at leastone of information about the voltage of the second shutoff devices 5A to5D, current of the second shutoff devices 5A to 5D, or the opened orclosed state of each the fourth switching unit 5 b.

In the above embodiment, the second shutoff devices 5A to 5D areconfigured to output the second state signals to the first shutoffdevice 4. However, the second shutoff devices 5A to 5D may output thesecond state signals to the inverter by power line communication orwireless communication. In this case, inverter 3 may determine anabnormality in the second shutoff devices 5A to 5D depending on thesecond state signals output from the second shutoff devices 5A to 5D andnotify that the second shutoff devices 5A to 5D are abnormal via thedisplay unit 10.

The first shutoff device 4 may output a first state signal to theinverter 3 via power line communication or wireless communication. Theinverter 3 may monitor the first shutoff device 4 based on the firststate signal output from the first shutoff device 4. When the inverter 3determines that the first shutoff device 4 is abnormal depending on thefirst state signal output from the first shutoff device 4, the inverter3 may output an abnormal signal to the display unit 10 or the user'smobile terminal to report that the first shutoff device 4 is abnormal.The first state signal output from the first shutoff device 4 may be thesame information as the second state signals output from the secondshutoff devices 5A to 5D. The first state signal output from the firstshutoff device 4 may be, for example, feedback to the inverter inresponse to the first shutoff device 4 outputting the command signal tothe first switching unit 4 a or the second switching unit 4 b inresponse to the first control signal, may include at least one ofinformation about the voltage of the first shutoff device 4, current ofthe first shutoff device 4, or an opened or closed state of the firstswitching unit 4 a or the second switching unit 4 b, or may includeinformation indicating that the first shutoff device 4 is abnormal.

The first control signal S1 and/or the second control signal S2 mayrepresent different types of information. That is, switching to theemergency safety shutdown mode can be determined not only by thepresence or absence of the first control signal S1 and the secondcontrol signal S2, but also by a certain type of information representedby the first control signal S1 and/or the second control signal S2.

For example, the first control signal S1 and the second control signalS2 may represent two types of values by binary numbers (referred to as afirst value and a second value). In this case, for example, when thefirst control signal S1 and the second control signal S2 exhibit thefirst value, switching to the emergency safety shutoff mode may bedetermined to be performed (the string 2 and the inverter 3 are cut off,and/or the connections between the solar cell module groups in thestring 2 are cut off). When the first control signal S1 and the secondcontrol signal S2 exhibit the second value, the switching may bedetermined not to be performed (the string 2 and inverter 3 are remainedconnected, and/or the solar cell module groups in the string 2 areremained connected).

The first control signal S1 and the second control signal S2 may beoutput at any time in modes other than the emergency safety shutoffmode, and the output of the first control signal S1 and the secondcontrol signal S2 may be stopped in the emergency safety shutoff mode.In this case, the first shutoff device and the second shutoff devicesturn ON the switching units when receiving the first control signal S1and the second control signal S2, and turn OFF the switching units whilenot receiving the first control signal S1 and the second control signalS2.

REFERENCE NUMERALS

-   -   1, 1′, 1″ Solar power generation system    -   2, 2′, 2″ String    -   3 Inverter    -   3 a DC/DC converter    -   3 b DC/AC inverter    -   3 c Control unit    -   3 d First control signal generating unit    -   4 First shutoff device    -   4 a First switching unit    -   4 b Second switching unit    -   4 c First signal receiving unit    -   4 d First driving unit    -   4 e First signal sending unit    -   5A to 5D Second shutoff device    -   5A′ to 5C′ Second shutoff device    -   5A″ to 5D″ Second shutoff device    -   5 a Third switching unit    -   5 b Fourth switching unit    -   5 c Second signal receiving unit    -   5 s Bypass circuit    -   5 e Power supply unit    -   5 f Second driving unit    -   5 g Bypass device    -   6 Solar cell modules    -   6A to 6H Solar cell module group    -   6A′ to 6D′ Solar cell module group    -   6A″ to 6S″ Solar cell module group    -   7 Power system    -   8 Operation switch    -   9 Commercial power supply    -   S1 First control signal    -   S2 Second control signal

1. A solar power generation system comprising: a string including aplurality of solar cell modules connected in series; an inverterconnected to the string and configured to convert DC power output fromthe string to AC power; a first shutoff device including a firstswitching unit and a second switching unit, the first switching unitconnected to an anode side terminal of the string and an anode sideterminal of the inverter, the second switching unit connected to acathode side terminal of the string and a cathode side terminal of theinverter, the first shutoff device configured to turn OFF the firstswitching unit and the second switching unit in response to a firstcontrol signal from the inverter; and a second shutoff device connectedto an electric path connecting a solar cell module group and eitheranother solar cell module or the inverter, the solar cell module groupincluding one or a plurality of solar cell modules connected in seriesin the string, the second shutoff device configured to cut off the solarcell module group and either the another solar cell module or theinverter in response to a second control signal from the first shutoffdevice, the second shutoff device further configured to output a secondstate signal to the inverter or the first shutoff device in response tothe second control signal from the first shutoff device.
 2. The solarpower generation system according to claim 1, wherein when the inverteror the first shutoff device determines that the second shutoff device isabnormal depending on the second state signal, the inverter or the firstshutoff device outputs an abnormal signal.
 3. The solar power generationsystem according to claim 1, wherein the second shutoff device outputsthe second state signal to the inverter or the first shutoff device bypower line communication.
 4. The solar power generation system accordingto claim 1, wherein the second shutoff device outputs the second statesignal to the inverter or the first shutoff device by wirelesscommunication.
 5. The solar power generation system according to claim1, wherein the second shutoff device includes an open-close unitconfigured to open and close a connection between the solar cell modulegroup and the another solar cell module, and the second state signalincludes information about an opened or closed state of the open-closeunit.
 6. The solar power generation system according to claim 1, whereinthe inverter is configured to monitor the first shutoff device based ona first state signal output from the first shutoff device.
 7. The solarpower generation system according to claim 6, wherein when the inverterdetermines that the first shutoff device is abnormal depending on thefirst state signal, the inverter outputs an abnormal signal.
 8. Thesolar power generation system according to claim 1, wherein the secondshutoff device includes a third switching unit and a fourth switchingunit, the third switching unit connected to an electric path connectingan anode side terminal of the solar cell module group and either theanother solar cell module or the inverter, the fourth switching unitconnected to an electric path connecting a cathode side terminal of thesolar cell module group and either the another solar cell module or theinverter.
 9. The solar power generation system according to claim 1,wherein the second shutoff device includes a bypass device connected inparallel with the solar cell module group and configured to form anelectric path bypassing the solar cell module group.
 10. The solar powergeneration system according to claim 9, wherein the bypass device is adiode having an anode connected to the cathode side terminal of thesolar cell module group and a cathode connected to the anode sideterminal of the solar cell module group.
 11. The solar power generationsystem according to claim 1, wherein the first shutoff device is drivenby power supplied from a commercial power supply.
 12. The solar powergeneration system according to claim 1, wherein the second shutoffdevice is driven by power generated by at least one of the plurality ofsolar cell modules.
 13. The solar power generation system according toclaim 1, wherein the inverter outputs the first control signal to thefirst shutoff device by power line communication.
 14. The solar powergeneration system according to claim 1, wherein the inverter outputs thefirst control signal to the first shutoff device by wirelesscommunication.
 15. The solar power generation system according to claim1, wherein the first shutoff device outputs the second control signal tothe second shutoff device by power line communication, upon receipt ofthe first control signal from the inverter.
 16. The solar powergeneration system according to claim 1, wherein the first shutoff deviceoutputs the second control signal to the second shutoff device bywireless communication, upon receipt of the first control signal fromthe inverter.